1. Field of the Invention
This invention relates to a bearing or rolling device which is adapted for use in spindle motors widely employed in peripheral information devices such as HDD (hard disk drive) and FDD (floppy disk drive) memories, CDD (compact disk drive), MOD (magneto-optical disk drive) and the like of computer systems, and VTR (video tape recorder).
2. Description of the Prior Art
In general, performances required for bearings, which are employed in peripheral information devices such as HDD (hard disk drive) and FDD (floppy disk drive) memories, CDD (compact disk drive), MOD (magneto-optical disk drive) and the like of computer systems, and VTR (video tape recorder), include a small torque, an excellent acoustic property, a long life, a reduced degree of dusting or scattering of grease, and the like.
Especially, with these information devices usually employed in a clean environment, it has been often experienced that a gaseous oil or fine particles of a grease scattered from the inside of a bearing at the time of rotation often cause the surfaces of a disk or the like to be contaminated, resulting in a malfunction of the device. Thus, it has been accepted as important the suppression of the amount of the scattered oil or grease. We have made extensive studies on this.
In recent years, a more serious problem has been closed up: when rolling devices, such as rolling ball bearings, particular roller bearings used in information devices, undergo vibrations at a low frequency of about 5 to 10 Hz caused during the course of carrying out and in of information devices or at the time of carrying such devices, race faces with balls or rollers inside a bearing suffer damages and are degraded, thereby causing a so-called fretting phenomenon.
When fretting takes place, the acoustic characteristics of the rolling ball bearing or roller bearing not only are worsened, but also adversely influence the performance of the information device.
It is an object of the invention to provide a rolling device for information devices which has not only a high performance and a long life while suppressing the amount of an oil or grease scattered from the rolling device, but also does not cause a fretting phenomenon.
It is another object of the invention to provide a rolling device for information devices which can satisfy the properties required for bearings used in peripheral information devices such as HDD (hard disk drive) and FDD (floppy disk drive) memories, CDD (compact disk drive), MOD (magneto-optical disk drive) and the like of computer systems, and VTR (video tape recorder), i.e. a small torque, an excellent acoustic property, a long life, a reduced degree of dusting or scattering of grease or oil during the course of high revolutions, and the like, and also can suppress a fretting phenomenon from occurring.
The above objects can be achieved, according to the invention, by a rolling device which comprises a plurality of rolling bodies provided between an outer member having a first contact face with each of the plurality of rolling bodies and an inner member having a second contact face with each of the plurality of rolling bodies, the plurality of rolling bodies individually being able to roll relative to the first and second faces, wherein a grease composition is sealedly filled inbetween the outer member and the inner member and comprises:
a carbonate compound of the following general formula (i) serving as a base oil (i) ##STR1## PA1 a lithium soap serving as a thickener; and PA1 at least one organomolybdenum compound selected from the group consisting of a molybdenum dithiophosphate of the general formula (ii) ##STR2##
wherein R and R' may be the same or different and independently represent a branched alkyl group having from 13 to 15 carbon atoms;
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represent an alkyl group having from 1 to 24 carbon atoms or an aryl group having from 6 to 30 carbon atoms, and a molybdenum dithiocarbamate of the general formula (iii) ##STR3##
wherein R.sup.5, R.sup.6, R.sup.7 and R.sup.8 independently represent an alkyl group having from 1 to 24 carbon atoms, and X represents O or S.